Running head: PREDICTING DELAYED LETTER KNOWLEDGE Predicting Delayed Letter Knowledge Development and its Relation to Grade 1 Reading Achievement among Children with and without Familial Risk for Dyslexia

The developmental trajectories of children’s early letter knowledge in relation to measures spanning and encompassing their prior language-related and cognitive measures and environmental factors and their subsequent Grade 1 reading achievement were examined. Letter knowledge was assessed longitudinally at ages 4.5, 5.0, 5.5, and 6.5 years, the preceding language skills and environmental factors at ages 3.5 and 4.5 years, and reading achievement at the beginning and end of Grade 1. The analyses were conducted on a longitudinal data set involving children with and without familial risk for dyslexia. Three separate clusters emerged from the trajectory analysis of letter knowledge; delayed (N =63), linearly growing (N = 73), and precocious (N = 51). The members of the delayed cluster were predominantly children with familial risk for dyslexia and the members of the precocious cluster were predominantly non-risk group children. In terms of language and cognitive skills, phonological sensitivity, phonological memory and rapid naming skills predicted delayed letter knowledge. Environmental predictors included level of maternal education and the amount of home-based letter name teaching. Familial risk for dyslexia made a significant contribution to the predictive relationships. Membership of the delayed cluster was a better predictor of poor reading performance at Grade 1 than membership of any of the alternative clusters.